In 1993, Olmstead wrote for the television series NYPD Blue. The series was created by Steven Bochco and David Milch. It focused on a single homicide unit in New York City. Olmstead eventually became an Executive Producer of NYPD Blue, and became a Producer in 2002.

Olmstead worked as a writer on the series Brooklyn South in 1997. The series was created by Milch and Bochco along with William M. Finkelstein and ex-police officer Bill Clark. The show detailed the lives of a single precinct of police patrol officers. Olmstead wrote four episodes for the series first season. The series was canceled after completing its first season.

He also worked as a writer and producer for NYPD 2069 in 2004. In 2005, he was one of the creators of the show Blind Justice. He wrote the Pilot and Episode 3. The show was canceled in June 2005 after just 13 episodes.

Olmstead is the showrunner of Chicago Fire joining the show as an executive producer after the show's pilot.[1] Olmstead has written a number of episodes and is an executive producer from episode 2 onwards.